why sye's ?

[crazymaci]

Why run an sye? A lot of what ive read says that 97-01 need it to cure vibration issues, and i thought i read at one point the driveline will pop out of the tcase , im asking is because i just got done putting 3.5" on my 2000. And have no vibration issues all the way up to 70mph, i did shim up the rearend 3deg.

 

[FilthyLlama]

When you lift everything except axles... you run the risk of the rear axle dropping farther away than your factory Slip Yoke can travel on your drive line and it will separate.

If you lift 3", your drive line angle changes and the maximum distance it can travel to make up for your axle traveling up and down stays the same...yet your xj is now able to send that axle further away... so an SYE eliminates that slip yoke (slip yoke eliminator).

I'm 98% sure along with an SYE you need to get a new drive line. One without a slipyoke that is longer than factory and connects to your rearend and the new sye.

I don't think at 3.5 you need to be worried. At 4.5+ you would need to be.

I could be absolutely incorrect about all things I just said

 

[FilthyLlama]

The vibrations are caused by extreme drive line angles. Those ujoints can only bend so fast. Some folks lower their transfer case to take the angle out. This eats up the clearance made by your lift so is counterproductive.

I imagine the shimming you did helps?

I'm hoping someone corrects me if I'm wrong lol

 

[WB9YZU]

3.5" should be fine with the stock driveline.

I wouldn't have shimmed the axle unless you took a reading of the driveline angles before installing the shim. Most folks drop the T-Case slightly instead as you may end up with the driveline angles equal and the same direction which will act poorly during acceleration. Rusty's make a drop crossmember which eliminates any loss in clearance.

With a single cardan shaft (1 u-joint on each end), the angles must be equal and opposite.

With a lift, you drop the rear axle and extend the driveline.
This can lead to problems with a standard slip yoke setup:
* Exceeding the length of the slip joint
* Exceeding the operational angle of the u-joints.
* Binding of the slip joint due to the angles involved.

Vibrations are genarally caused by:
* Incorrect driveline angles
* Unbalanced driveline
* Exceeding the operational angle of the u-joints.

Many XJ owners install a SYE and Double cardan shaft to eliminate vibrations without even looking at why; they just do it.

A SYE - Slip Yoke Eliminator, is a fixed yoke on the output of the Transfer Case. Because you eliminated the slip joint, you then need to install a drivehaft with a slip joint in the driveline.

Most folks install a driveline with a single and a double cardan joint, and a slip joint at the axle end (just like the front). The DC joint divides the 2 u-joints angles and produces a smooth rotation. You align it just as the front. A small bit of pinion down from straight line on the rear u-joint.

So a cheap version of a SYE would be a GM Yoke which you make fixed (I forget the P/N) and a front driveshaft. See the gojeep site for details on his SYE

 

[crazymaci]

Ok i see, i do have an advance adapters sye kit, and a double cardon driveshaft from rough country, once i test drove and didnt have any vibes i was wondering if i freed up 500 dollars for another upgrade, though i do want to do it right and eliminate a future problems

 

[XJJeepNewb]

A few years ago i put on the complete 4.5 RE lift and hadn't initially planned to do the SYE ,driveshaft and shims.....one drive from the shop about 40 miles away to the house cured me of that notion.

On my 99 (231, auto, 8.25 rear) the vibrations and noise were headache-inducing, I couldn't imagine driving it that way and the tcase drop seemed like a mediocre way to fix the problem. YMMV.

 

[Brandon77]

I have the RE Long Slip Yoke - RE1822

http://www.rubiconexpress.com/Drivetrain-Differentials/Slip-Yoke-Long.aspx?t_c=12&t_s=515&t_pt=8407&t_pn=R%2FERE1822

 

[crazymaci]

Front driveshaft huh? Is there a specific type, i hear a manual gearbox xjs have a longer front driveshaft,is this the one you speak of? How do they hold up, ive read that a lot of you guys run that way

 

[NCCherokee]

4.0l with aw4 and np231 front driveshaft is basically the same length as the shaft you'll need after an SYE, unless you get one of those TJ super short sye. I used my front shaft in the rear while I waited on my new shaft to be built after I did my SYE.

 

[X E Ryder]

As long as the rear axle pinion is "looking" right at the xfer case output shaft (pinion angle wise) with an SYE, you should be vibration free (it allows the cardan to roll without rest of the shaft hopping).

I run an SYE I got from OMIX, Tom Woods shafts, and have 4.56 gears on 33's - I drive 60 mph no problem or vibes.

You can tell the driveshaft is hauling a$$ tho!

 

[Boost_Retard]

when I lifted my 01 3.5" I got the stock driveline running parallel and vibe free with 2.5° shims and no T case drop.. I thought I was going to get away without the SYE but after a few months of daily drive I ended up getting a growl sound that was coming from my slip yoke, it being pulled out so far from the t case ended up wearing out the splines on the slip yoke.

I then went with the SYE/woods combo and some 4° shims (installed opposite direction compared to no SYE setup) and it now runs vibe free growl free

i would not get rid of your sye stuff right away...

 

[sidriptide]

I have the RE Long Slip Yoke - RE1822

http://www.rubiconexpress.com/Drivetrain-Differentials/Slip-Yoke-Long.aspx?t_c=12&t_s=515&t_pt=8407&t_pn=R%2FERE1822

that is basically a YJ slip yoke. check your local jeep club bulletin boards for a used one. most guys will give it away for free.
take not of the shape of the yoke on the RE unit, it is a deep "U" shape. some YJs came with a shallow "square" yoke that doesnt give enough clearance. i ran a 4.5" RE lift in my 90 XJ with no shim and a YJ yoke with good results including a 5500 mile road trip to Moab.

 

[kenny811]

You can look at it like this, o you want to be that guy? The guy who dropped is rear drive line out of the transfer case. SYE you eliminate all doubt.

 

[WB9YZU]

You must have never seen a slip joint shaft separate on the trail.
I've seen it twice. One was a front shaft, the other a rear shaft.

It's all in the planning. If you put the frame on jackstands and put the suspension in droop and you still have a good inch of splines or more left in the slip joint or slip yoke, you should be good to go.

There is a thread around here by a fellow who had a DS made with a long slip yoke, but used a double cardan joint at the T-Case side. He still had to shim the axle to correct the rear pinion angle for the DS, but it worked just fine.

I have also seen SYE yokes with a single cardan shaft with a slip joint. That worked for what he wanted it for.

 

[crazymaci]

Im going to put my sye in, i already have it,and i dont want to be "that" guy, i also plan on going taller in the future so ill just eliminate any future doubt. I think i will return the rough country driveshaft and get the tom woods one.